1. Field of Invention
The present invention relates to equipment for manufacturing semiconductors. More particularly, the present invention relates to a multi-functional conditioner set for a chemical-mechanical polishing station.
2. Description of Related Art
Chemical-mechanical polishing is one of the most important techniques for global planarization of very-large scale integration (VLSI) and ultra-large scale integration (ULSI) circuits.
FIGS. 1A and 1B are respective top and side views of a conventional chemical-mechanical polishing station. As shown in FIGS. 1A and 1B, a chemical-mechanical polishing station includes a polishing table 10, a holder 11, a polishing pad 13, a delivery tube 14, a pump 16 and a conditioner 17. The holder 11 is used for gripping a silicon chip 12 to be polished. The polishing pad 13 is a layer of polishing material over the polishing table 10. The delivery tube 14 is used to deliver slurry 15 to the polishing pad 13. The pump 16 pumps slurry 15 from a slurry container to the delivery tube 14. The conditioner 17 serves to roughen the surface of polishing pad 13, to remove any residual slurry and to clean. To conduct chemical-mechanical polishing, both the polishing table 10 and the holder 11 rotate in a pre-defined direction shown by arrows 18a and 18b. The holder 11 grips the backside 19 of the silicon chip 12 so that the front side 20 of the chip 12 is pressed onto the polishing pad 13. The pump 16 drives slurry 15 through the delivery tube 14 so that the polishing pad 13 receives a stable supply of slurry 15. Since any protruding portions on silicon chip surface 20 are in contact with the polishing pad 13, the protruding portions are removed with the assistance of chemical agents and abrasive particles in the slurry 15. Hence, a planarized surface is obtained after repeated chemical and mechanical polishing actions.
In general, a polishing pad has tiny holes for assisting the polishing process and the transmission of slurry. In addition, the polishing pad has a roughened surface whose height varies between 1 to 2 xcexcm for easy gripping of the chip surface and transferring slurry. However, after a few polishing operations, the rough polishing pad surface may be planarized leading to a lost in the capacity for gripping, slurry transport and pressure. Consequently, the rate of polishing is likely to drop. At the same time, some of the holes in the polishing pad may be clogged by polishing material (such as particles in the slurry or materials removed from the silicon wafer). Hence, the polishing rate is difficult to maintain. Under such circumstances, the conditioner 17 is needed to re-condition the polishing pad surface so that clogged holes are cleared and the rough surface re-constituted. Conditioning can be carried out after wafer polishing or in tandem with the wafer polishing operation.
Polishing pads can be divided into two major types including a hard polishing pad and a soft polishing pad depending on applications. To condition the hard polishing pad, a diamond conditioner and a nylon conditioner are both required because the hard polishing pad is very hard. Together with de-ionized water from the conditioning pipeline, the diamond conditioner is able to reconstitute the roughened surface of a polishing pad necessary for polishing. Together with de-ionized water or chemical agents delivered by the conditioning pipeline, the nylon conditioner is able to clear away clogging material or leftover diamond particles inside the holes of a polishing pad. In contrast, only a nylon conditioner is needed when conditioning the soft polishing pad.
A conventional chemical-mechanical polishing station can accommodate just one operating conditioner at any one time. Since the conditioner needs to be exchanged when conditioning a hard polishing pad, servicing time is likely to increase, leading to in a longer manufacturing cycle. One method of reducing conditioning time for a hard polishing pad is to set up two working conditioners on the polishing station at the same time. FIG. 2 is a sketch showing a conventional chemical-mechanical polishing station having two conditioners. However, using an additional working conditioner on the polishing pad congests the polishing table and may lead to difficulties in synchronizing some operations. In addition, although the conditioning pipeline in a conventional chemical-mechanical polishing station can deliver de-ionized water or chemical agents, the de-ionized water or chemical agents do not include any ultrasonic or megasonic vibrations. Therefore, the full capacity of de-ionized water or chemical agents in conditioning a polishing pad is not utilized.
Accordingly, one object of the present invention is to provide a multi-function conditioner set for a chemical-mechanical polishing station. The multi-function conditioner set includes a plurality of conditioner heads each made from a different material so that the processing cycle is shortened and area occupation of the station is reduced. The supply of chemical agents and de-ionized water with ultrasonic or megasonic vibration increases their conditioning capacity to full power. By combining different conditioning heads individually or a plurality of different conditioning heads as groups and using the chemical agents or de-ionized water with ultrasonic or megasonic vibration, a used polishing pad can be re-conditioned and cleaned without causing any conventional technical problems.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a multi-functional conditioner set. The multi-functional conditioner set includes a plurality of conditioning heads and an ejection tube having a vibrator thereon. Materials constituting the conditioning heads differ according to the applications such as roughening, removing polishing material or cleaning (including removing residual diamond dust on the polishing pad). Conditioning heads can be made from materials including diamond particles or nylon. Size and shape of the conditioning heads also depend on application. All the conditioning heads can have identical size or shape or different sizes and shapes. The conditioning beads may be, for example, round, oval linear or cruciform in shape. To operate the multi-functional conditioning heads, pneumatic valve system or a motor is used to activate different combination of heads in each conditioning session according to the type of conditioning required. The ejection tube for delivering chemical agents or de-ionized water is connected to a vibrator. The vibrator is able to induce molecular vibration in the chemical agents or de-ionized water so that sufficient energy is imparted upon the chemical agents or de-ionized water to dislodge polished particle from the polishing pad. In this invention, different results are therefore obtained by using different combinations of conditioning heads and different vibration settings of the vibrator attached to the ejection tube.
The multi-functional conditioner set of this invention group combines together a plurality of conditioning heads with an ejection tube. By combining different single conditioning heads or a plurality of conditioning heads and adjusting the ejection tube settings in different conditioning sessions, conditioning and cleaning of a polishing pad and removal therefrom of residual diamond particles can be conducted sequentially without switching conditioners.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.